Corrosion resistant copper-zinc alloy



Patented Jan.30,1940

' UNITED STATES PATENT OFFICE CORROSION RESISTANT COPPER-ZINC -ALLOY No Drawing.

5 Claim.

.This invention relates to improvements in copper-zinc alloys, and has for an object to make them more resistant to corrosion, in particular to make them more resistant to dezincification,

without reducing their other desirable character-.

istics such as workability, strength, etc.

Copper-zinc alloys in the form of rod, wire, tube, sheet, plates, castings and forgings are used extensively in one form or another for marine fittings, condenser tubes, heat exchangers, plumbing, welding and brazing, Fourdrinier wire, bolts, screws, screw machine products and stampings, and for many other uses where the metal must resist corrosion.

The copper-zinc alloys containing approximately from 58% to 85% copper without and with additions of up to about 3.5% of tin, aluminum, lead, iron, manganese and silicon either alone or in various combinations undergo a type of corrosion known as dezinciflcation under some conditions of corrosive attack. Dezinciflcation may occur as the result of a more or less uniform corrosion of the metal surface or may occur as local attack over scattered areas with a consequent rapid penetration of the metal. The latter type of attack is often referred to as plug type dezincification and often makes the use of copper-zinc alloys unsatisfactory.

The generally accepted theory for dezincification postulates that the metal dissolves as an alloy and the\ opper replates or-deposits on the surface of the copper-zinc alloy as a porous mass having very little tensile strength.

It -is therefore an object of this invention to impart to certain copper-zinc alloys superior corrosion resistance, and in particular resistance to dezincification, so that they will have longer life and be much less apt to iail when used in,

one form or another for marine fittings, condenser tubes, heat exchangers, plumbing, welding and brazing, Fourdrinier wire, bolts, screws screw machine products, and stampings and, in fact, for any other product where the metal must resist corrosion, particularly where dezinciflcation is a factor.

We have found that if a small amount of silver is added to copper-zinc alloys and copper-zinc alloys containing up to about 3.5% of either tin, aluminum, lead, iron, manganese, or silicon, or additions of two or more of these elements, dezincification is hindered or entirely prevented. For example, we have found that an alloy containing approximately 70% copper and 0.04% silver, the remainder zinc does not 'dezincify under conditions which will cause an alloy of similar Application March 20., 1939. Serial No. 263,062

composition, but substantially free from silver, to dezincify. We have also discovered that amounts of silver less than 0.04% silver, as low as 0.01%

.and in some cases less than 0.01% as 0.005%

will be beneficial, and that amounts as large as 5 approximately 2% may be used, but from about 0.02% to about 0.2% is generally sufficient.

Silver additions in amounts varying from approximately 0.005% to 2.0% may also be added to copper-zinc alloys containing aproximately 58% to 85% copper with additions up to 3.5% of tin, aluminum, lead, iron, manganese, or silicon, or of two or more of these elements.

The preferred range of silver is from about 0.02% to about 0.75%, but generally from about 0.02% to about 0.2% is sufficient to give the desired effect, and from the standpoint of cost it is desired to keep the silver content as low as. possible and still secure the desired efiect.

These alloys with the addition of the silver can be used for making the same articles as could the same alloy without the silver. Thus these alloys can be hot and cold worked, forged, etc. and made into the shapes and worked in the same way as the same alloys without the silver. In other words the wcrkability 'of these .alloysis not essentially changed by the addition of the silver.

Thus certain of these alloys may be hot or cold rolled into rod, plate, sheet, strip, and in so fact, all shapes made by rolling. Certain of them may be formed by drawing through dies into wire, rod, tube, and other shapes. Some of them may be forged hot or cold by die pressing or similar v operations and some of them may be extruded through dies to form simple shapes like bars and rods and into more intricate forms, generally known as architectural shapes.

Certain of these alloys may be cast in sand I molds or in permanent molds either under at- 40 mospheric pressure or under higher pressure such as used in diecasting processes.

Some of these alloys may be welded or brazed and are suitable for types of articles fabricated by either gas welding or electric welding or both, and some may be used in the form of wire, rod, or powder for welding or brazing.

Certain of these alloys in the form of sheet or other usable form may be drawn, stamped, pressed or spun into all forms made by these processes, such as, for example, shells, cups and diaphragms.

The wire or strip made from some of these alloys may be woven or formed by some other process into screens or similar products.

Because of their superior corrosion resistance, and in particular their resistance to dezinciflcation, they may be used in one form or another for marine fittings, condenser tubes, heat exchangers, plumbing, welding and brazing, Fourdrinier wire, bolts, screws, screw machine products, and stampings and in fact, for any other product where the metal must resist corrosion, particularly where dezinclflcation is a factor.

Having thus set forth the nature of our invention, what we claim is:

1. A copper-zinc alloy containing from approximately 58% to 85% copper, 0.005% to 2.0% silver, and the remainder zinc.

2. A copper-zinc alloy containing from approximately 58% to 85% copper, 0.02% to 0.2% silver,

and the remainder zinc.

3. A copper-zinc alloy containing from approximately 58% to 85% copper, silver in amount. suiflcient to secure increased resistance to dezinci flcation and up to 0.75%, and the remainder zinc.

4. A copper-zinc alloy comprising approximately 58% to 85% copper, 0.005% to 2% silver, re-

mainder substantially all zinc, and which is characterized by increased resistance to dezincification JOHN R. FREEMAN,

Jii. ARTHUR w. TRACY. 

